fix: mesh mobile header hidden + DID hover on node names

- Mesh: remove display:flex from .mesh-header CSS that overrode
  Tailwind hidden class, causing title/peers to show on mobile
- Federation: add title={did} on node name for hover tooltip
- Cloud: add title={did} on peer name for hover tooltip
- Both already show node.name when available, DID as fallback

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/views/Mesh.vue

@@ -782,7 +782,7 @@ function truncatePubkey(hex: string | null): string {
 }
 
 .mesh-header {
-  display: flex;
+  /* display handled by Tailwind hidden md:flex */
   justify-content: space-between;
   align-items: center;
   gap: 16px;